MIDAS-GEN_Flat_Slab_tutorial.pdf

Contents
Step 1: Model & Automesh
Step 2: Design Parameters
Step 3: Member Design
Step 4: Slab/Wall Design
Automesh and Slab/Wall Design Tutorial
Midas Information Technology Co., Ltd.

Overview
Step
00
9 m 16 m 9 m 23 m
5
m
6
m
7
m
2
m
12.5
m
Typical Floor Plan
3
m
3
m
3
m
3
m
3
m
Sectional Elevation

Eurocode-1:2005
• Beam : Concrete Grade C25/30
• Column: Concrete Grade C25/30
• Wall: Concrete Grade C30/37
Designation Story Section Number
Column Dimension
(mm)
Column 1~5F 2 400 x 400
Designation Section Number
Section Dimension
(mm)
Girder 1 500 x 400
Designation Thickness Number
Thickness Dimension
(mm)
1 200
2 250
Step
00
Girder sections
Column section dimension
Wall thickness
Materials
Applied Code
Details of the Building

Load Details
Dead Load Self Weight Weight Density: 1 kN/m3
Live Load Pressure Load
Shopping areas : 4.0 kN/m2
Office areas : 2.0 kN/m2
Wind Load X-dir./ Y-dir.
Eurocode-1(2005)
Terrain Category : II
Response
Spectrum Load
X-dir./ Y-dir.
Eurocode-8(2004)
Spectrum Parameters: TYPE 1
Ground Type : B
Importance Factor : 1.0
Step
00 Details of the Building
Applied Load

Step
01
Procedure
2
3
1 File > Open Project…
Select “flat slab.mgb”.
Click [Open] button.
Opening the Pre-generated Model File
3
Opening the Pre-generated
Model File 2

Procedure
Model > Mesh >
Auto-mesh Planar Area
Method : Line Elements
Type : Quad + Triangle
Mesh Size : Length : 0.5 m
Material : 1:C25/30
Thickness : 1:0.200
Domain : 1
Select by Window > Front View
Select Roof-Line
Iso View > Click [Apply]
1
Step
01
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
Generate meshed elements for slabs
Specify meshed area for auto-
meshing (Line elements method).

Procedure
Top View >
Select Wall-Line
Activate > Iso View
Method : Planar Elements
Material : 2:C30/37
Thickness : 2:0.250
Domain : 2
Select Wall > Click [Apply]
Domain : 3
Select Wall > Click [Apply]
1
Step
01
2
3
4
5
6
1
2
3
4
5
6
Generate meshed elements for walls
meshing (Line elements method).

Procedure
Step
01 Auto-mesh Planar Area
Model >
User Coordinate System >
X-Z Plan
Origin : 39, 4, 0
Click : [Apply] > [Close]
Model > Grids >
Define Point Grids
dx, dy : 1, 1
Click : [Apply] > [Close]
1
2
3
4
1 3
4
2
Generate meshed elements with
opening
meshing (Nodes method).

Procedure
Step
01 Auto-mesh Planar Area
Model > Mesh >
Auto-mesh Planar
Method : Nodes
Material : 2:C30/37
Thickness : 2:0.250
Display Node Numbers
(Toggle On)
Domain : 4
Click Nodes >
Click : [Apply] > [Close] >
Activate All
1
2
3
4
5
6
1
2
3
4
5 6
Generate meshed elements with
opening
meshing (Nodes method).

Procedure
Tree Menu > Work >
Domain1 [1] > Double Click
Load > Pressure Loads
Load Case Name : LL
Direction : Local z
Loads : P1 : -4.0kN
Shopping areas
D1 : Areas in general retail shops
Click [Apply] > [Close]
1
Step
02
2
3
4
5
1
2
3
4
5
Pressure Loads
6
6
Apply floor loads

Procedure
Tree Menu > Work >
Domain1 [2] > Double Click
Load > Pressure Loads
Load Case Name : LL
Direction : Local z
Loads : P1 : -2.0kN
Office areas
Click [Apply]
1
Step
02
2
3
4
5
1
2
3
4
5
Pressure Loads
6
6
Apply floor loads

Procedure
Model > Building >
Building Generation
Number of Copies : 4
Distance(Global z) : 3 m
Operations : Click [Add]
Select All > Click [Apply]
1
Step
02
2
3
4
5
1
2
3
4
5
Building Generation

Procedure
Model > Building > Story >
Auto Generate Story Data
Select
Click [OK]
Click [Close]
1
Step
02
2
3
4
1 4
Auto Generate Story Data
2
3

Procedure
View > Activities >
Active Identity
Click : Story > 4F
Click : [Active] > [Close]
1
Step
02
2
3
1
Active Identity
2
3

Procedure
Model > Domain >
Define Sub-Domain
Click : [2]
Rebar Dir.(CCW) :
Dir.1 : 135, Dir.2 : 135
Click : [Modify] > [Close]
1
Step
02
2
3
4
1
Define Sub-Domain
4
2
3
Define sub-domain for design
Reinforcement direction can
be specified by sub-domains.

Procedure
Load > Lateral Loads >
Wind Loads > Click [Add]
Load Case Name : WX
Wind Load Code :
Eurocode-1(2005)
Wind Load Direction Factor :
X-Dir. : 1, Y-Dir. : 0
Click [Apply]
Load Case Name : WY
Wind Load Direction Factor :
X-Dir. : 0, Y-Dir. : 1
Click [OK]
Click [Close]
1
Step
02
2
3
4
5
6
1
2
3
4
5
6
7
7
Wind Loads

Procedure
Load > Response Spectrum
Analysis Data > Response
Spectrum Functions
Click [Add]
Click [Design Spectrum]
Design Spectrum :
Eurocode-8(2004)
Spectrum Type :
Horizontal Design Spectrum
Click [OK]
Click [OK]
Click [Close]
1
Step
02
2
3
4
5
6
1
7
Response Spectrum Functions
2
3
4
6
5
7
8
8

Procedure
Load > Response Spectrum
Analysis Data > Response
Spectrum Load Cases
Load Cases Name : RX
Excitation Angle : 0
Check : EURO2004 H-Design
Click [Add]
Load Cases Name : RY
Excitation Angle : 90
> Click [Add]
Click
[Eigenvalue Analysis control] >
[OK]
Click [Close]
1
Step
02
2
3
4
5
6
1
Response Spectrum Load Cases
7
2
3
4
6
5
7

Procedure
Results > Combinations >
Concrete Design >
Auto Generation
Click [OK], Click [Close]
Perform Analysis
1
Step
02
2
3
1
2
3
Auto Generation

Step
03
Procedure
Design >
Concrete Design Parameter>
Concrete Design Code
Click [OK]
Design >
Concrete Code Design >
Column Design
Sorted by : Member >
Click [Close]
1
2
1
2
3
4
3
4
Column Design

Step
03
Procedure
Design >
Concrete Design Parameter>
Modify Column Rebar Data
Main : P32
End : P16@200 / Center : P16
Click [Add/Replace] > [Close]
1
2
1
3
Modify Column Rebar Data
2
3

Step
04
Procedure
Design >
Meshed Slab/Wall Design >
Slab/Wall Load Combinations
Click [OK]
1
2
1
2
Slab/Wall Load Combinations
Slab/Wall Load Combination
Select the load combinations for
the slab/wall element design.

Step
04
Procedure
Design >
Design Criteria for Rebar
For Slab Design :
Angle 1 : 0.03 m, 0.03 m
Angle 2 : 0.05 m, 0.05 m
Click [OK]
1
2
3
1
2
3
Design Criteria for Rebar
Specify rebar size
Enter the standard sizes of
rebars used in the design of
reinforcement for slab/wall
elements.

Step
04
Procedure
View > Activities >
Active Identity
Click : Story > 3F
Check : +Below
Click : [Active] > [Close]
1
2
3
Active Identity
2
3
1

Step
04
Procedure
Design >
Slab Flexural Design
Select [Avg. Nodal].
Check [As_req(m^2/m)]
Check on One-Way Flexure
Design option and click […]
button
Defined Cutting Lines [Add]
Click [Apply]
1
2
3
1
3
4
Check the flexural design results
for slab elements in contour.
4
5 6
5
 Display the bending moments
of the floor slab elements along
a cutting line, and produce the
design results of reinforcement.
2
6

Step
04
Procedure
Design >
Click [Design Result]
Click [Design Force]
Click [Update Rebar]
1
2
3
4
1
3
4
5
 Produce the detail flexural
design results of slab elements
in a text format.
 Produce the flexural design
forces of slab elements in a
tabular format.
 Update the rebar quantity for
each slab element. The updated
rebar data is used for strength
verification.
5
2

Step
04
Procedure
Design >
Check [Resistance Ratio]
Load Cases/ Combinations
: cLCB5
Check [Dir.1]
Click [Apply]
Click [Update Rebar]
1
2
3
4
5
1
2
3
5
6
 The ratio of the design moment
to the moment resistance when
the designed rebar spacing is
applied.
6
4
7
7

Step
04
Procedure
[Smoothing]
For practical design, smooth moment distributions are preferred. By selecting the smoothing option, the
program can consider the smooth moment in slab design.
Element: Design results are displayed using the internal forces calculated at each node of elements.
(no smoothing)
Avg. Nodal: Design results are displayed using the average internal nodal forces of the contiguous elements
sharing the common nodes.
Element: Design results are produced for moments at each node of slab elements. (no smoothing)
Width: Design result of slab elements at each node is produced using the average of the bending moments of
the contiguous slab elements with the specified width.
(Example) Design force for Node. EN21
In one plate element, 4 internal forces exist. For the element E2,
member forces exist at the node EN21, EN22, EN23 and EN24.
Following equations show how the smoothing option works for
the node EN21. (Assume that rebar direction is selected as Angle 2
for Width smoothing direction.)
(1) Element + Element: EN21
(2) Avg. Nodal +Element: (EN12+EN21+EN33+EN44)/4
(3) Element + Width 2m: (EN11+EN12+EN21+EN22)/4
2m
1
2
EN73
EN72
EN83
EN82
(4) Avg. Nodal + Width 2m: {(EN11+EN34+EN72+EN83)/4 + (EN12+EN21+EN33+EN44)/4
+ (EN22+ EN43+ EN51+EN64)/4 }/3
Avg. Nodal of EN33 =
(EN12+EN21+EN33+EN44)/4
Width 2m of EN33 =
(EN33+EN34+EN43+EN44)/4
2m
Average Nodal and Width smoothing
Design > Meshed Slab/Wall Design >

Step
04
Procedure
Design >
Check [Wood Armer Moment]
Load Cases/ Combinations
: CBC : cLCB6
Check [Dir.1]
Click [Apply]
1
2
3
4
5
1
2
3
4
5
 Display the Wood Armer
Moments in contour.

Step
04
Procedure
[Wood Armer Moment]
From the analysis results, following plate forces about the local axis are calculated
- mxx
- myy
- mxy
In order to calculate design forces in the reinforcement direction, angle α and φ will be
taken as following figure:
x, y: local axis of plate element
1, 2: reinforcement direction
α: angle between local x-direction and reinforcement direction 1
φ: angle between reinforcement direction 1 and reinforcement
direction 2
Firstly, internal forces (mxx, myy and mxy) are transformed into the a-b coordinate system.

Step
04
Procedure
[Wood Armer Moment]
Then, Wood-Armer moments are calculated as follows:

Step
04
Procedure
Design >
Slab Shear Checking
Click [Apply]
1
2
1
2
Slab Shear Checking
Slab Shear Checking
Produce the two-way shear
(punching shear) check results at
the supports of slab elements or
at concentrated loads and the
one-way shear check results
along the user-defined Shear
Check Lines.

Step
04
Procedure
[Punching Shear Check(By Force)]
Slab Shear Checking
In this method, the program takes the axial force in the column supporting the slab as the shear force (V_Ed).
The basic control perimeter (u1) is taken at a distance 2d from the column face (as shown in the diagram below.
The maximum shear force is calculated by multiplying V_Ed with shear enhancement factor β. The value of β is
different for different columns. (as given in the code)
The shear resistance of the slab (without shear reinforcement) at the basic control section is given by
V_Rd,c = (0.18/γ_c)k(100*ρl*fck)1/3*(u1*d) , the value of ρl is assumed to be 0.02.
If
•V_Ed < V_Rd,c : section is safe in punching shear
•V_Ed > V_Rd,c : provide shear reinforcement.
Asw/sr = (v_Ed-0.75*v_Rd_c)*(u1*d) / (1.5*d*fywd_ef)

Step
04
Procedure
[Punching Shear Check(By Stress)]
Slab Shear Checking
In these methods (The Stress Method), the Shear force along the critical section is taken and divided by the
effective depth to calculate shear stress.
Therefore there is no need to calculate β (Beta), to consider moment transferred to the column.
(There are 4 plate elements intersecting at nodes. The nodes are marked by nomenclature of Grid Lines. As the
center node is denoted by B2 , B on x-Axis and 2 on Y-Axis)
When slab is defined as the plate element, the program calculated stresses only at the nodes, in the analysis. So
we have the stresses at B1, B2, C2 etc. (see the figure above) are calculated by the program.
Case 1 - To calculate stresses at the critical section that is u1 in the given figure, for example we take the point P
in the figure which lies in a straight line. The stress at B1 and B2 are known. The values at these nodes are
interpolated linearly to find the stress at point P .
Case 2- Now if the point lies in the curve such as the point Q, then the software will divide the curve into 6 parts.
At each point such as Q a tangent which intersects B1-B2 and C2-B2.The value of stresses at T and V are
determined by linear interpolation of stresses which are known at for T (at B1 and B2) and for V (at C2 and B2).
After knowing stresses at T and V the stress at Q is determined by linear interpolation of stresses at T and V.

Step
04
Procedure
Slab Shear Checking
(Method 1: Average by elements.)
In this method the stresses at all the critical points is determined. The critical points divide the critical section
into segments. The average value for all these segments is determined by dividing the stresses at the two ends
of the segment by 2. After determining the average value for each segment, the maximum average value
from all of the segments is reported as the Stress value for the critical Section.
a,b are stresses at the segment ends.
Average value for the segment will be (a+b)/2, and such average value for each segment is determined.

Step
04
Procedure
Slab Shear Checking
(Method 2: Average by Side)
In this method stresses at all critical points is determined and then average stress value is calculated by weighted
mean.
To calculate weighted mean , For example we have 4 critical points a, b, c, d.
- Stress at critical points: For example at ‘a’ its 9
- Average of the segment: For example in ‘a’ and ‘b’ its
(15+9)/2 = 12
- Distance Between the critical points: For example
between ‘a’ and ‘b’ its 8
- Final Stress = (12 * 8 + 17 * 10 + 15 * 6)/ (8+10+6), which
is the weighted average.
We divide the Critical section into 4 sides as shown in figure.
The weighted mean value for each side is determined and then
the maximum value out of the 4 sides A, B, C, D is reported as
the stress value.

Step
04
Procedure
Design >
Concrete Design Parameter >
Serviceability Parameter
Select All
Click [Apply]
1
2
1
2
Serviceability Parameter
3
3

Step
04
Procedure
Design >
Serviceability Load
Combination Type
Click [OK] > [Close]
1
2
Serviceability Load Combination Type
1
2
Serviceability load combination
type is automatically assigned if
‘Auto Generation’ function has
been used to generate load-
combinations.
If the user manually defined
load combinations, serviceability
load combination type must be
defined by the user. If
serviceability load combination
type is not specified, Slab
Serviceability Checking is not
performed.

Step
04
Procedure
Design >
Slab Serviceability Checking
Check [Stress Checking]
Check [Concrete]
Click [Apply]
1
2
1
3
Produce the serviceability check
results for slabs.
3
4
4
 Display the compressive stress
in the concrete.
5
2
5

Step
04
Procedure
1
3
4
6
Design >
Check [Crack control]
Check [Crack Width]
Select [Value]
Click [Apply]
1
2
3
4
 Display the value of crack
width.
 Crack control is not performed
for slab elements for which
thickness is less than 200mm.
2
5
5
6

Step
04
Procedure
Design >
Check [Deflection]
Check [Creep]
Select [Value]
Click [Apply]
1
2
1
3
3
4
4
Calculate the deflection for the
uncracked section and compare
it with the allowable deflection
(deflection for the cracked
section is not available yet) .
6
2
5
6
5

Step
04
Procedure
2
4
5
Wall Design
View > Activities > Active All
Design >
Wall Design
Check [As_req(m^2/m)]
Select [Resistance Ratio].
Click [Apply]
1
2
3
Wall Design
Perform the flexural design
results for wall elements in
contour.
 Display the area of the
required reinforcement.
 Wall design is performed
based on EN 1992-1-1:2004
Annex F (Tension reinforcement
expressions for in-plane stress
conditions).
3
4
5

Step
04
Procedure
Design >
Wall Design
Click [Design Result]
Click [Design Force]
1
2
3
1
2
3
Wall Design

MIDAS-GEN_Flat_Slab_tutorial.pdf

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